The characteristics of the fluorescence and phosphorescence emission of 2-amino-4 (3H) pteridinone (or pterin) in aqueous solutions are pH dependent. The room temperature fluorescence quantum yield is low and is maximum at pH = 10 (& -0.057). The 77 K phosphorescence emission consists of two overlapping emissions originating from z,n* triplet states. In agreement with low temperature results, the 353 nm laser flash photolysis makes it possible to detect at pH 9.2, two transient triplet absorptions (T, -0.3 ps and T~ -2.3 p). The longer lived triplet is characterized by z 0.20 and eT. (550nm) = 2000 M -' cm-'. It reacts with the solvent forming the semireduced pterin with a quantum yield d R -0.06. The photosensitizing properties of pterin have been studied by laser flash spectroscopy and steady state irradiations. Photoreactions implying singlet oxygen formation are shown to occur. Laser flash spectroscopy indicates that the pterin triplet is reduced by amino acids and nucleic acid bases. Corresponding bimolecular reaction rate constants have been measured.PROPERTIES OF 2-AMINO-4 PTERIDINONE:

No abstract

No abstract

Ferritin is the principal protein of iron storage (in the Fe(III) state). The UV-A irradiation of 0.25 microM ferritin solutions (from horse spleen) loaded with 530 microM Fe(III) induces Fe2+ release in the medium. The initial quantum yield is wavelength dependent (phi(365 nm) approximately 2 x 10(-3) but pH and oxygen independent. The Fe2+ release reaches a plateau which strongly depends on pH and oxygen. The amino acid composition of the apoprotein is not altered by the UV irradiation. Addition of formate ions enhances the Fe2+ production, suggesting that the ferritin photoreduction involves an electron transfer from an OH- ligand. The possible importance of this phenomenon in skin photobiology is discussed.